Electronic taximeters are known including a microprocessor and volatile working memory which is backed up by a permanent supply of D. C., said memory containing, in particular, unit prices for taxi occupation time and for distance traveled, on the basis of which the microprocessor calculates the cost of a trip.
These prices vary from one place to another, and within a given location they need updating frequently.
Programming boxes are known which contain a computer unit and memories into which new charging data is inserted. Each taximeter includes input/output (I/O) connectors enabling it to be connected to I/O connectors on the programming box, and the external computer unit contained therein is programmed to communicate with the taximeters using a specific dialog protocol. During the dialog, the external computer unit clears the working memory of the taximeter connected thereto and transfers new charging data therein taken from its own memory.
PLESSEY's French Pat. No. FR 76/37,706 (published under the U.S. Pat. No. 2,335,892) describes taximeters and an apparatus for loading them, said apparatus including a microprocessor, a keyboard, memories, and an interface circuit enabling successive taximeters to be connected to the charging apparatus and enabling charging data to be transferred into the taximeters.
The use of programming boxes or apparatuses for loading taximeters with charging data is under the control of official bodies whose task is to monitor measuring and charging apparatuses and such use is authorized only for said bodies or for persons authorized thereby.
This solution requires a large number of programming boxes to be constructed, e.g. one or more per large town, together with accurate surveillance of the way in which they are used.
When programming boxes are numerous, there is an increase chance of fraud by non-authorized persons, who may be able to obtain a programming box and use it to insert increased unit prices into taximeters.
The object of the present invention is to provide means which are cheaper and more secure for reprogramming all of the taximeters within the jurisdiction of a given authority.
Telecommunications networks exist, such as the TRANSPAC network, which enable so-called "server" central computers to be called from telephone sets which are associated with local terminals, e.g. terminals including a keyboard, a display screen, and a "modem", i.e. a modulator-demodulator enabling binary signals to be transmitted over telephone lines in the form of audio frequencies compatable with such lines.
A terminal may be constituted, for example, by a small computer equipped with a "modem". Once a connection has been established, the server sends packets of information to the local terminal and the local terminal may display the information on its screen.
As a general rule, a local terminal (whether a dedicated telecommunications terminal or a computer fitted with a modem) includes an interface fitted with an I/O connector suitable for connection to a printer for printing the information which appears on the screen.
The user of such a network dials a number using a telephone set which puts the user in communication with the network. The user then keys in a code on the keyboard of the terminal to be connected to a given server. Thereafter, the user may need to key in a password specific to the user in order to enable the server to identify the caller so that the services provided may be billed.
All the above is well known.